The present invention relates to a disk apparatus for recording and reproducing digital continuous data such as video data or audio data, and more particularly, to a video disk apparatus for alternately recording and reproducing data by time sharing.
Developments have been made to a video disk apparatus for recording and reproducing a digital video image into and from a storage medium, such as an optical disk or the like, using video compression, such as a Moving Picture Experts Group (MPEG) method.
According to a video disk apparatus using a conventional optical disk, digital video data compressed by MPEG encoder as a digital video compressor or digital video data supplied by broadcasting or CATV (cable television) is once stored into a buffer memory in which an adjustment is made on a difference between the bit rate (which means the bit capacity transferred per second) of the digital video data inputted and the recording/reproducing speed (which means the bit capacity recorded/reproduced per second) of an optical disk. Normally, the bit rate of inputted digital video data is slower than the recording/reproducing speed of an optical disk.
As for a practical form of using such a video disk apparatus, it will be very advantageous for practical use if a video image once recorded can be reproduced during recording. For example, a user who comes back home while a program is being recorded by a recorder that had been set by a timer may wish to watch the program from the beginning while the program is still being recorded.
However, in a conventional video disk apparatus, a video image can be reproduced only after the recording of the image is completed. Thus, it is not possible to simultaneously reproduce a video image while recording the video image. In order to solve this problem, a conventional apparatus comprises independent optical heads for recording and reproducing, respectively, thereby to realize a simultaneous recording/reproducing function. This method, however, results in an increase in costs since a plurality of optical heads are used.